In this paper, two new series of main-chain and side-chain second-order nonlinear optical (NLO) polyurethanes have been successfully prepared, in which isolation groups with different sizes were introduced to adjust the NLO property of the resultant polymers, according to the concept of "suitable isolation groups". The second harmonic generation (SHG) experiments demonstrated that all the polymers exhibited large second harmonic generation (SHG) coefficients of d33 values (up to 105.6 pm/V) with excellent thermal stability and filmforming ability, indicating that the introduction of isolation groups could alleviate the "nonlinearity-stability trade off" efficiently. In addition, for both main-chain and side-chain polymers, BOP acted as the suitable isolation group. It was also found that the positive influence of the linked suitable isolation spacer was more obvious in the main-chain polymers, in comparison with those in the side-chain polymers.

XPush-pull indole-containing nonlinear optical chromophores with different acceptor and ð-conjugated moieties have been synthesized and characterized. Experimental measurements of the second-order nonlinear optical response demonstrated that the chromophores exhibit similar or superior optical nonlinearity compared with their analogues with an aniline moiety as the donor group, but the indole-based chromophores display blueshifted absorption, even up to 30 nm.

Two series of polyurethanes (P1-P10) containing NLO chromophores as side chains were prepared, in which the size of isolation groups was changed from small atoms to much larger groups such as carbazolyl groups. The polymers were well characterized. The tested NLO properties of the polymers demonstrate that the NLO values and the poling efficiency of the polymers are not always improved with increasing of the size of isolation spacer, and for a given chromophore moiety, there is a suitable isolation group present to boost its microscopic â value to possibly higher macroscopic NLO property efficiently.

A series of nonlinear optical (NLO) chromophores were successfully prepared, in which pyrrole moieties were the conjugated bridge. In comparison with their analogues containing furan or thiophene groups as the bridge, these chromophores demonstrated similar or enhanced NLO effects (up to 3.3 times) and interesting optical behavior. While the acceptor groups were malononitrile (Mal), 3-phenyl-5-isoxazolone (Iso), and 1,3-diethylthiobarbituric acid (Bar), the chromophores exhibited much blue-shifted maximum absorption wavelengths (ìmax) (up to 36 nm); however, the ìmax of the chromophore containing tricyanovinyldihydrofuran (TCF) as acceptor became much longer than that of the analogue (up to 75 nm).